1. Field of the Invention
The present invention relates to a manufacturing method of a silicon substrate, and more particularly, to a technique suitable for manufacturing a silicon substrate used for manufacturing a solid-state imaging device by improving gettering capability.
Priority is claimed on Japanese Patent Application No. 2008-054842, filed on Mar. 5, 2008, the content of which is incorporated herein by reference.
2. Description of the Related Art
A semiconductor device such as a solid-state imaging device made of silicon is manufactured by forming a circuit on a silicon substrate sliced from a silicon single crystal pulled by a CZ (Czochralski) method or the like. When heavy metal impurities are incorporated into the silicon substrate, white spots occur due to dark current. Due to the white spots, device characteristics of the solid-stage imaging device significantly deteriorate.
Heavy metal as impurities is incorporated into the silicon substrate by the following two causes: metal contamination during a manufacturing process of a silicon substrate including pulling of a single crystal, slicing, chamfering, and surface treatments such as polishing, grinding, and etching; and heavy metal contamination during a manufacturing process of a device such as a thinning process by scraping the rear surface of a wafer down to about 50 μm after forming the circuit on the silicon substrate.
In JP-A-6-338507, a technique for reducing white spots generated due to dark current that affects electrical characteristics of a solid-state imaging device is disclosed. In addition, an example of an IG (intrinsic gettering) method of forming an oxygen deposit on a silicon substrate is also disclosed. In JP-A-2006-313922, an EG (extrinsic gettering) method of forming a gettering site such as backside damage on the rear surface of a silicon substrate, and a technique related to carbon ion implantation are disclosed.
As described above, as a manufacturing method of a silicon substrate used for a solid-state imaging device, the IG (intrinsic gettering) method of forming an oxygen deposit by performing an oxygen precipitation heat treatment before epitaxial growth is known.